# For Loops [basic]

Discussion in 'C' started by k3y, Mar 9, 2012.

1. ### k3yNew Member

Joined:
Mar 9, 2012
Messages:
14
2
Trophy Points:
0
Occupation:
Student
Hey guys,
I just learned the basics of FOR loops and felt maybe I should share for fellow n00bs out there. A FOR loop can in many cases replace a WHILE loop. This tutorial will show you the relationship between the WHILE loop and the FOR loop, as well as an exercise that I found to be very helpful in learning how to utilize them.
Syntax of a WHILE loop:

Code:
```i = 1; // initializer
while (i <= 10) // condition
{
cout << i << " ";
i++; // increment
}
```
Now in a FOR loop

Syntax of a FOR loop:
Code:
```for (i=1; i <= 10; i++) //initializer; condition; increment
cout << i << " ";
```
Now as you can see the FOR loop is much more condensed then the WHILE loop, and saves some headache. Now it's time for an example code (test a number for primeness):
Code:
```#include <iostream>
#include <math.h>
using namespace std;
int main()
{
int n;
bool is_prime = true; // boolean (assumes true)

cout << "Enter a number and press ENTER: ";
cin >> n;

for (int i = 2; i <= sqrt(n); i++)
{
if (n % i == 0) // if the remainder of n divided by i is zero
is_prime = false; // then n is not prime
}

// Print result

if (is_prime)
{
cout << "Number is prime." << endl;
}
else
{
cout << "Number is not prime." << endl;
}
return 0;
}
```
Here are a few good exercises to get yourself familiar with WHILE and FOR.
Exercises:
- optimize this program
- find the correct place to put a break statement
- make the same program using a WHILE loop

Hope this can help someone

shabbir likes this.